1. PC21 Coal Retirement Study
TAS/TEPPC – Nov. 2015
WECC System Adequacy Planning
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2. Western Electricity Coordinating Council
Study Requestors
Center for Energy Efficiency and Renewable Technologies (CEERT)
Natural Resource Defense Council (NRDC)
PacifiCorp (PAC)*
State and Provincial Steering Committee (SPSC)
Scenario Planning Steering Group (SPSG)
Western Grid Group (WGG)
Western Interconnection Regional Advisory Body (WIRAB)
*PAC later withdrew from study request when scope was changed to indefinitely postpone a reliability analysis.
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Overview
Study Description
Scope
Input assumptions
Study qualifications
Study Results
Details
Generation
Paths
Other
Observations
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Study Description
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5. Study Description - Purpose
Model a scenario that approaches the 2024 trajectory of reducing carbon emissions to 80% below the 2005 levels by 2050.
248 in 2024
This trajectory has a 34% reduction by 2024 and a 44% reduction by 2030.
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6. Study Description - Assumptions
Modeling assumptions include:
Retirement of several high CO2 intensity coal-fired generators based on vintage and location
Addition of renewable resources (wind + solar)
Additional energy efficiency
Addition of gas-fired generation
Addition of energy storage resources
More details on next slides
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7. Western Electricity Coordinating Council
PC21 Additional Coal Retirements AB AZ CA CO MT UT WY
Battle River
4,5 [537]
Apache 2,3 [350]
ACE Cogen [103]
Comanche 1,2 [660]
Colstrip 1,2,3 [1354]
Huntington 1,2 [909]
Dave Johnston 1-4 [762]
Genesse 2 [390]
Cholla 1,3 [387]
Argus 8,9
[50]
Craig 1,2
[863]
Intermountain 1,2 [1800]
Jim Bridger 1,2,3 [1581]
Sheerness 1,2 [780]
Coronado 1 [380]
Casterville
[1]
Hayden 1,2 [446] NM
KUCC 1-4
[175]
Naughton 1,2 [357]
Sundance 3 [362]
H.W. Sundt 4 [156]
Fellow
M Drake 5,6,7 [254]
Four Corners 4,5 [1540]
Sunnyside
[53]
Neil Simpson 2 [80]
Navajo 2,3 [1500]
Jackson Valley [21]
Nucla 1-4 [100]
Wygen 1,2 [180]
Lassen
[22]
R D Nixon 1 [208] NV WA
Wyodak
[340]
Mt Poso
[35]
N Valmy 2 [268]
Centralia 2 [688]
Phillips Carbon [16]
TS Power 1 [227]
Portland Cement [28]
Port of Stockton [44]
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8. Western Electricity Coordinating Council
PC01 Common Case Coal Retirements [6418 MW] AB AZ CA CO MT UT WY
Battle River 3 [148]
Cholla 2
[262]
RioBravo Jasm [35]
Arapahoe 3,4 [153]
JE Corette [153]
Carbon 1,2 [172]
Neil Simpson 1 [18]
HR Milner [144]
Four Corners 1-3 [560]
Cherokee 3 [152]
Osage 1-3
[30]
Sundance 1,2 [576]
Navajo 1
[750]
Lamar 4,6
[38] NM
Valmont 5 [184]
San Juan 2,3 [839]
WN Clark 1,2 [40] NV WA
Reid Gardner 1-4 [587]
Centralia 1 [688]
Valmy 1
[254] OR
Boardman [610]
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9. PC21 Coal Retirements by State/Province
These are summations by state/province of the capacity and energy from the PC01 Common case v1.5. The lower capacity factor of the Utah retirements is related to the direct impact of AB32 on the Intermountain Generating Station.
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10. Western Electricity Coordinating Council
Replacement Sources
The Retired MWh represents the energy produced by the PC21 retired coal resources in the 2024 v1.5 common case. The EE energy was modeled as a load reduction and resulted in a total reduction of about 1700 GWh.
The estimated energy values for CC, CT, and ES are based on the assumed capacity factors in the bottom table. Note that the replacement assumptions only replace 53% of the energy that was retired. Will there be any unserved load?
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Study Qualifications
Path Ratings: The WECC paths associated with a few of the retired generators and their replacements would likely need to be re- rated through the path rating process. No changes in path or branch ratings were assumed for this study.
Constraints: Other operating constraints and nomograms were also not modified.
Flexibility Reserves: The flexibility reserve adders for each reserve area are derived from the loads and amount of variable generation. The flexibility reserve adders were not recalculated for this study.
Resource Adequacy: A check of the peak planning reserve margins was not done.
System Stability: Tests of system stability were not conducted.
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Results
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Dump Energy
Generation that is chosen by the PSM model for commitment and dispatch for a least-cost solution may be dumped if its dispatch will break a modeling constraint regarding generation, transmission, reserves, and/or nomograms.
Reserves
Nomograms
Cost
Deliverable
Constraints
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From New Gen
269,923
2,409,645
1,801,747
Load side
18,820,604
38,636,263
61,938,182
-1,731,070
This is a summation of the annual generation by category for the PC01 (common case) and the PC21 (coal retirement case), showing the differences between the two cases. The table on the right (blue heading) provides the portion of the change that came from the PC21 replacement resources. Keep in mind that additional EE was applied to reduce the loads in AZ, NM, NV, UT, and WA.
629,356
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15. Category Change – Estimated/Actual
This is a graphical comparison of the change for a few categories relative to the PC21 replacement units and the PC01 units that were carried forward. The floating blue marker shows the estimated energy for the replacement units; the red bar shows the resultant energy from the replacement units; and the green bar shows the change from the “carried forward” units.
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17. Generation Comparison
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18. Difference in Annual Energy - WECC
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19. 2024 CO2 PC21 Coal Retirement Case
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20. Generation Change by State and Fuel
Provides the changes from the retirements, the replacements, and the redispatch.
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21. Western Electricity Coordinating Council

22. Western Electricity Coordinating Council
The chart shows the relationship of the pump storage operation with the LMP price. Negative denotes pumping and positive denotes generating periods.
This was the only replacement ES unit that had any significant operation. The others didn’t seem to reach the price thresholds.
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WECC Paths
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24. Top 15 Heavily Utilized in PC21
General practice is to ignore paths 52 and 60 since they are low voltage and controllable via phase shifters. The minor congestion on path 83 is from Alberta to Montana.
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25. Comparison of Net Annual Flow – Top 15 U90
Note that a few paths had a reversal of net annual flow.
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26. PC-21 Heavily Utilized Paths
P83 Montana Alberta Tie Line
Path
75%
90%
99%
P60 Inyo-Control 115 kV Tie
38%
25%
18%
P52 Silver Peak-Control 55 kV
34%
23% 0%
P83 Montana Alberta Tie Line
20%
11% 7%
P52 Silver Peak-Control
P60 Inyo-Control
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Path 8
The retirement of the base load generation at Colstrip 1,2,3 had an impact on the Path 8 flows. It is also possible that the path rating would be reduced.
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28. Western Electricity Coordinating Council
Path (COI plus PDCI)
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29. Western Electricity Coordinating Council
Path 27
In the past a nomogram has been used to define a relationship between generation and path 27 flows. The nomogram was not modified to specify how the replacement generation in Utah would be treated with respect to southern California.
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Path 46
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More Results
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WECC Peak Week
Interesting here how much the simple-cycle combustion turbines were dispatched. Next slide shows the percentage breakdown for the peak hour.
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WECC Peak Hour – PC21
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34. Western Electricity Coordinating Council
WECC Early April
Windy month. A lot of ramping of base-load coal units. Late peaks = 8:00 pm or 9:00 pm
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Dump Energy 4/7/24 – PC21
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36. Peak hour on April 2 – WECC PC21
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California Peak Week
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38. California Early April
The dump energy here is likely from over-generation due to must-take generation and generator constraints in California and also in the interconnected regions.
The gaps between the demand and generation represent energy imports. The hours where the generation exceeds the demand represents exports.
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Imports are negative; exports positive.
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Observations
The PC21 study had no unserved load.
PC21 CO2 was 29 million metric tons short of goal
Overall energy from PC01 CC and CT units increased
Overall energy from remaining coal units increased
Share of annual energy from renewable resources is 23.1% in PC21 vs. 17.7% in PC01
Poor performance of PC21 pump storage projects except for project added in SRP area
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Contact
Stan Holland
Western Electricity Coordinating Council
Senior Engineer
(801)
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